Contents lists available at ScienceDirect International Journal of Greenhouse Gas Control journal homepage: www.elsevier.com/locate/ijggc Gas phase amine depletion created by aerosol formation and growth Hammad Majeed, Hanna Knuutila, Magne Hillestad, Hallvard F. Svendsen ⁎ Norwegian University of Science Technology, Trondheim 7491, Norway ARTICLE INFO Keywords: Post combustion CO 2 capture Absorption columns Aerosol formation Amine emissions Internal droplet profiles Gas phase profiles Orthogonal collocation method Simulation ABSTRACT Aerosols are systems of droplets or wet particles suspended in gases. In post combustion CO 2 absorption systems aerosols can be formed by spontaneous phase transitions in supersaturated gas phases or by droplets or particles entering the absorber with the gas to be treated. Micron and sub-micron mist droplets and fog formed in these processes cannot be removed by conventional demisting devices and because amine may be absorbed in the droplets this may increase dramatically the amine emissions from absorption columns as reported previously (Khakharia et al., 2015; Schaber et al., 2002). Thus, it is important to understand the mechanisms governing droplet growth and amine uptake through absorber as well as the effect large numbers of aerosol droplets can have on the bulk gas phase composition. A model developed and implemented in Matlab, predicts how the gas phase composition and temperature change along the absorber taking into account mass and heat transfer to and from both the bulk liquid and the droplet phase. The objective of this work, compared to earlier work, Majeed et al. (2017), is to study the possible effect of gas phase component depletion on the droplet growth and droplet internal variable profiles and how this varies with initial droplet size and composition, droplet number concentration and amine volatility. For MEA, as a relatively volatile solvent it is seen that gas phase depletion already takes place at number concentrations above 10 5 droplets/cm 3 with an initial droplet radius of 1.5 μ and 5 M MEA initial concentration. For initial droplet radius 0.15 μ and 0.0001 M MEA initial concentration, which may be a more realistic case, hardly any depletion effect is seen up to 10 7 droplets/cm 3 . With change in amine volatility it is seen that the gas phase depletion effect is significantly stronger in the case of low volatility than for MEA at high droplet number concentrations. It is found that gas phase amine depletion has a strong effect on droplet growth. 1. Introduction Very rapid growth in energy consumption was experienced in the 20th century and with an increasing world population and per capita use, it is expected that significantly more energy will be needed in the 21st century. Meeting these demands by the use of fossil fuels in power production and industrial processes is one main contribution to climate change by accumulation of greenhouse gases (GHGs) and in particular CO 2 in the atmosphere. Post combustion CO 2 capture (PCCC) by chemical absorption is one of the most developed technologies for capturing CO 2 from low pressure emissions (Abu-Zahra, 2009; MacDowell et al., 2010; Rochelle, 2009; Sanchez-Fernandez et al., 2013). Solvent emission in the form of aerosols is one of the main challenges for widespread implementation of such plants (Schaber et al., 2002; Khakharia et al., 2015) as amine emission to air may impose a potential risk to human health and pro- duce possible negative effects on the environment, as indicated by studies reported in (Knudsen and Randall, 2009). In depth studies performed in the Gassnova CCM projects, see Fullskala Mongstad (2014), that possible consequences with full scale operation using MEA on environment will be very small. Detailed experimental data on aerosol droplet growth and emissions do not yet exist. Analytical measurements techniques such as Fourier Transform Infrared Spectrometry (FTIR) and Phase Doppler inter- ferometry (PDI) can be used to estimate overall emissions and particle size distributions (Fulk, 2016; Fulk and Rochelle, 2013). These methods give overall measurements but do not give insight into aerosol behavior inside the absorbers. Therefore, a detailed simulation tool is required that is able to predict aerosol formation and development as function of operational and chemical characteristics. Since the physical conditions in a gas–liquid contactor are very complex, it is necessary to use a somewhat simplified model to understand the behavior. A basic simu- lation tool for the description of a single aerosol droplet development in CO 2 absorption columns is already established and described in Majeed http://dx.doi.org/10.1016/j.ijggc.2017.07.001 Received 6 April 2017; Accepted 5 July 2017 ⁎ Corresponding author. E-mail addresses: hammad.majeed@ntnu.no (H. Majeed), hanna.knuutila@ntnu.no (H. Knuutila), magne.hillestad@ntnu.no (M. Hillestad), hallvard.svendsen@ntnu.no (H.F. Svendsen). International Journal of Greenhouse Gas Control 64 (2017) 212–222 1750-5836/ © 2017 Elsevier Ltd. All rights reserved. MARK